1. Technical Field
This invention relates to a reactor for hydrotreating which contains plural catalyst layers (catalyst beds) packed with hydrotreating catalysts respectively, and to a process for producing an ultralow sulfur heavy oil from a heavy oil containing sulfur compounds and metallic components by the use of the reactor.
2. Description of the Prior Art
There has been known a process which comprises using a fixed bed reactor packed with two kinds of hydrotreating catalysts, i.e., a demetallization catalyst and a desulfurization catalyst and bringing a heavy oil such as an atmospheric or vacuum distillation residue of a crude oil having high sulfur content into contact with the hydrotreating catalysts to thereby lower the sulfur content of the heavy oil, thus producing a low sulfur heavy oil for a long period. When a heavy oil having high sulfur content is used in the above process as the feed oil, however, the reactor is poor in total desulfurizing activity, so that the oil thus produced still has such high sulfur content as to be unsatisfactory in performance. Even when an atmospheric distillation residue having low sulfur content was used in the above process as the feed oil, there occurred the problem that the total desulfurizing activity of the reactor lowered too rapidly to operate the reactor for a long period, though an ultralow sulfur heavy oil could be temporarily produced in some cases by elevating the reaction temperature. Thus, the processes of the prior art had the disadvantage that the total desulfurizing activity of the reactor was too poor to produce an ultralow sulfur heavy oil over a long period.
An object of this invention is to provide a reactor for hydrotreating which contains plural catalyst layers packed with hydrotreating catalysts respectively and which exhibits a total desulfurizing activity higher than that of the reactor according to the prior art, which is reduced in the rate of lowering of the desulfurizing activity and therefore can keep the high desulfurizing activity over a long period, and to provide a process for producing an ultralow sulfur heavy oil from a heavy oil containing sulfur compounds, metallic components by the use of the reactor.
The inventors of this invention have intensively studied for the purpose of solving the above problems, and as a result of the studies, they have found that a reactor for hydrotreating which contains plural hydrotreating catalyst layers having specific relationship to each other exhibits a total desulfurizing activity higher than that of the reactor of the prior art and that the high total desulfurizing activity of the reactor of this invention is so slowly lowered as to be kept at a high level over a long period. This invention has been accomplished on the basis of these findings.
Namely, this invention provides a reactor for hydrotreating, which comprises at least four catalyst layers packed respectively with hydrotreating catalysts satisfying the relationship represented by the following formulae:
Snxe2x89xa6Sn+1 xe2x80x83xe2x80x83(1) 
1.15Vnxe2x89xa7Vn+1 xe2x80x83xe2x80x83(2) 
wherein S represents the surface area per cubic meter of each hydrotreating catalyst: V represents the pore volume per cubic meter of catalyst; and wherein n is a natural number representing the order of each catalyst layer.
Further, this invention also provides a process for producing an ultralow sulfur heavy oil, which comprises using the reactor for hydrotreating of this invention, and passing a heavy oil through the first to the last catalyst layers successively to thereby bring the heavy oil into contact with hydrogen gas under hydrogenation conditions in each catalyst layer.